The present invention relates to dynamic bone fusion devices and associated techniques and, more particularly, to such fusion devices and associated techniques for effecting optimal spinal fusion.
It is known generally that, according to Wolff""s law, every change in the form and function of a bone, or in its function alone, is followed by certain definite changes in its internal architecture and secondary alterations in its external conformation.1 Based on this principle and others, dynamic bone fusion devices and procedures are designed to simulate strain conditions in which compressive forces are applied to the junction of bone segments to be fused, thereby initiating and sustaining fusion.
1Stedman""s Medical Dictionary, 26th Ed, 1995 
The success rates of fusion depend on a variety of factors including the location and types of bones to be fused, and the techniques and devices used. There currently does not exist specific available data and correlating guidelines on the types of devices and techniques that, for a given set of parameters, provides ideal or optimum strain or loading conditions to initiate and sustain high success rate dynamic fusion. Nor does there currently exist specific available data for identifying ideal strain and loading conditions for vertebral dynamic fusion.
It is an object of the present invention to provide devices and associated techniques for initiating and sustaining optimum dynamic bone fusion procedures and, particularly, such procedures for vertebral fusion. These objects and others are achieved by the present invention described herein.
The present invention is directed to dynamic fusion devices, such as spinal implant devices for vertebral fusion, that are selected within the parameters of available data and modeling to determine optimum ranges of strain and loading for initiating and sustaining highly successful rates of fusion. In summary, various available data for a variety of fusion cases has been analyzed and is used as a basis for modeling the fusion conditions of vertebrae. Specifically, data available from intra medullary nail systems is used with beam deflection principles to arrive at stiffness constants and applicable strain conditions for ideal states in which high fusion success rates are likely.